JP2001309183A - Image processing unit and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing unit that can copy a color image in a short time without causing deterioration in the image quality. SOLUTION: The image processing unit that reads an original image as a digital color image signal and forms an output color image of the original image, is provided with a 1st filter means that applies prescribed digital filter processing to the color image signal to reduce image deterioration after image compression, a means that compresses and stores the color image signal after digital filter processing, a means that expands the stored color image signal, and a 2nd filter means that applies prescribed digital filter processing to the color image signal after the expansion to reduce the image deterioration after the expansion. The output color image is formed on the basis of the color image signal from the 2nd filter means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image processing system, and more particularly to an image processing system capable of efficiently controlling the input and output of color image data with high image quality.

[0002]

2. Description of the Related Art As a device for digitally reading a color document image to generate a copy image, a so-called color document copying device as shown in FIG. 10 is conventionally known.

In FIG. 10, reference numeral 1001 denotes an image scanner which reads an original and performs digital signal processing. Reference numeral 1002 denotes a printer unit;
This portion prints out an image corresponding to the document image read by the image scanner 1001 on paper in full color.

In the image scanner 1001, 10
Reference numeral 00 denotes a mirror pressure plate. A document 1004 on a platen glass 1003 is irradiated by a lamp 1005, and its reflected light is guided to mirrors 1006, 1007, and 1008, and a three-line solid-state image sensor ( An image is formed on a CCD 1010, converted into three image signals of red (R), green (G), and blue (B) as full-color information, and processed by the signal processing unit 101.
Sent to 1. Note that a lamp 1005, a mirror 1006
Is speed v, mirror 1007 and mirror 1008 are speed 1
/ 2v electrical scanning of line sensor 1010 (main scanning)
The entire surface of the document is scanned (sub-scanning) by mechanically moving in the direction perpendicular to the direction. Here, the original 1004
Is 400 dpi (dots / inc.) For both main scanning and sub-scanning.
It is read at h) resolution.

[0005] In a signal processing unit 1011, the read image signal is electrically processed, decomposed into components of magenta (M), cyan (C), yellow (Y), and black (Bk). Send to 1002. In the image scanner 1001, M, C, Y, B
k are read one by one and sent to the printer unit 1002. Therefore, by scanning the document four times in total, 1
The printout of one manuscript is completed.

The M, C, Y, and Bk image signals sent from the image scanner unit 1001 are sent to a laser driver 1012. The laser driver 1012 is
The semiconductor laser 1013 is modulated and driven according to the transmitted image signal. The laser light is reflected by a polygon mirror 1014,
The photosensitive drum 1017 is scanned via an f-θ lens 1015 and a mirror 1016. Here, similarly to the reading, writing is performed at a resolution of 400 dpi (dots / inch) in both the main scanning and the sub-scanning.

Reference numeral 1018 denotes a rotary developing unit, which includes a magenta developing unit 1019, a cyan developing unit 1020, and a yellow developing unit 1
21 and a black developing section 1022, the four developing sections alternately contact the photosensitive drum 1017, and develop the electrostatic latent image formed on the photosensitive drum with toner.

Reference numeral 1023 denotes a transfer drum, which winds a sheet supplied from a sheet cassette 1024 or 1025 around the transfer drum 1023 and transfers an image developed on the photosensitive drum to the sheet.

After the four colors M, C, Y, and Bk are sequentially transferred in this manner, the sheet is fixed to the fixing unit 1026.
, The toner is fixed on the sheet, and the sheet is discharged.

In a conventional color original copying apparatus, an image scanner unit 1001 for reading an original and a printer unit 1002 for outputting a copied image are operated in conjunction with each other. That is, after the reading process by the CCD sensor 1010 is completed, the process up to the fixing by the fixing unit 1026 is executed without interruption. In addition, reading of the manuscript
It is performed four times continuously for each of the colors M, C, Y, and Bk. Similarly, image formation is also performed for each color.

[0011]

However, in the conventional color original copying apparatus, since the scanner section and the printer section need to be linked, when the printer section is in a standby state, the copying operation and the original reading operation are not performed. There was a problem that it could not be done. Further, when copying a plurality of copies of each of a plurality of documents, the user has to read a plurality of times in accordance with the number of copies to be output for each document, so that there is a problem that the user takes a long time to read.

In order to cope with such a problem, the reading process of the document is performed only once instead of continuously, and the read image data is temporarily stored in the storage means, and the M, C, Y,
A configuration in which the stored image data is read out and output in synchronization with the image formation of each Bk is also conceivable.

However, in general, since the capacity of each image data is enormous, there has been a problem that an enormous storage capacity is required to store a plurality of original images in the storage means at one time. In addition, there is a problem that a huge storage capacity is required when a plurality of document images need to be read at once, such as when replacing pages of a plurality of document images or performing composite output. There is also a problem that it is not easy to perform layout synthesis or the like by enlarging or reducing data. Further, a configuration in which the image is compressed by a method such as JPEG or the like and the data is collectively stored in a large-capacity storage means such as a hard disk can be considered, but there has been a problem in that the image quality is deteriorated due to the image compression.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and has as its object to provide an image processing apparatus and method capable of copying a color image in a short time without deteriorating image quality. I do.

[0015]

In order to achieve the above object, the present invention provides an image processing apparatus for reading an original image as a digital color image signal and forming an output color image of the original image. First filter means for performing a predetermined digital filtering process on the image signal, means for image-compressing the color image signal after the digital filtering process, and storing the color image signal after the image compression Means for expanding the stored color image signal, and second filter means for performing a predetermined digital filtering process on the expanded color image signal, wherein the first filter Means for reducing deterioration of the color image signal after the image compression.
The second filter means performs digital filter processing for reducing deterioration of the decompressed color image signal, and performs the output color processing based on the color image signal from the second filter means. An image is formed.

According to another aspect of the present invention, there is provided an image processing apparatus for sampling a document image in pixel units and reading the digital image signal as a digital color image signal to form an output color image of the document image. Identification means for identifying an image feature at each pixel position based on a signal pattern; flag generation means for generating predetermined flag data for each pixel according to the identification result; and a plurality of digital filters The first fill means having characteristics and individually performing fill processing, and the color image signal output from the first fill means and having different fill processing are used to convert the flag data for each pixel into the flag data. A first forming unit for extracting the color image signal and forming the color image signal, and image-compressing the formed color image signal. A compression unit that also compresses the flag data, a unit that stores the color image signal after the image compression and the flag data after the data compression, and a unit that stores the stored color image signal and the stored flag data. Decompression means, second filter means having a plurality of digital filter characteristics and individually performing filter processing, and different color image signals from the filter processing output from the second filter means. A second forming means for extracting the color image signal in accordance with the decompressed flag data for each of the pixels to form a color image signal, wherein the color image signal from the second forming means is provided. To form the output color image.

In another aspect of the invention, the first filter means and the second filter means change the plurality of digital filter characteristics in accordance with a magnification.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] An image processing apparatus according to a first embodiment of the present invention will be described below.

FIG. 1 is a block diagram showing the configuration of the image processing apparatus according to the first embodiment of the present invention.

<Reading Unit> The document to be copied is placed on a document table (not shown) of the scanner unit 101 and read. As in the case of FIG. 10, the scanner unit 101 digitally reads a document image for each pixel using a color three-line CCD, and transfers a color image signal to the input image processing unit 102. In the input image processing unit 102, the scanner unit 1
01 for the RGB color image signal sent from
Known image processing such as shading correction, CCD line-to-line correction, and color correction is performed.

Reference numeral 103 denotes an image area block for performing a filtering process on the input image processed color image signal output from the input image processing unit 102, and is a feature of the present invention.

The details of this filter section will be described later.

<Storage of Image Data> Image data read by a scanner and subjected to various input image processing is 10
4 is temporarily stored in the image memory 1. At this time, the image data is stored as an entire document page or as a partial image of a predetermined size in one page. The temporarily stored image data is compressed by the data compression unit 105 and stored in the storage device 106. It is desirable that the storage device 106 is a high-speed storage device such as a semiconductor storage device. JPE is used for image data compression.
It is irreversible like compression by G irreversible method,
It is desirable to use a high-efficiency compression method in which image degradation considering human visual characteristics is less noticeable.

However, even in JPEG compression, image degradation may occur at a portion such as an edge portion. The filter 1 103 plays a role of suppressing this deterioration.

As described above, the image data subjected to different compression processing is stored in the storage device 106 in units of one page of the document. The stored data may also be written to 107 auxiliary storage. In the auxiliary storage device 107,
Preferably, a medium such as a hard disk, which has a slightly lower recording speed but can store a large amount of data, is used. This makes it possible to efficiently store and store a large number of pages of document images.

<Reading of image data> Storage device 106
Alternatively, the image data stored in the auxiliary storage device 107 is
The data is read for output to the printer unit, the compressed data is decompressed by the data decompression unit 108, and is written to the image memory 2 109.

<Output of Image Data>

The image data temporarily stored in the image memory 109 is transferred to the filter 2 110 when it reaches a predetermined size. The processing of the filter 2 at 110 is also described later, similarly to the processing of the filter 1 at 103.

Upon receiving the output of the filter 2 at 110, the output image processing unit 111 converts the luminance and density from RGB to CMYK in order to print out the RGB image data.
A known image processing such as conversion into gamma correction, binarization processing, etc. is performed, and the image data is transferred to the printer unit 112.

The printer unit 112 receives the transferred CMYK
Is driven based on the image signal of (1), a visible image is formed on a transfer sheet in the same procedure as in the case of FIG.

<Filter> The details of the filter section, which is a feature of the present invention, will be described.

As described above, the image may be deteriorated even by the compression method such as JPEG. The deterioration occurs remarkably in a place where there are many high-frequency components such as an edge portion. The sharpness of the high frequency component is a very important factor that affects the quality of the output image.

Therefore, in the filter 1 of 103, the JPE
A smoothing filter coefficient having a characteristic of reducing high frequency components is used so as to prevent image deterioration due to G compression.

Also, the filter 2 of 110 has a characteristic of raising the high-frequency component dropped by the filter 1 from a filter coefficient which originally has a characteristic of correcting MTF deterioration or the like caused by a lens or a CCD. Edge enhancement filter coefficients are used.

As described above, in the embodiment of the present invention, since the above-described configuration is employed, the handling of images in the color image processing system is facilitated, without imposing a great burden on the user, and in the image storage means. By realizing an image system in which the capacity of the image data is reduced and providing filters before and after data compression and decompression, it is possible to obtain a high-quality image output with less image deterioration due to compression.

[Second Embodiment] Hereinafter, a second embodiment of the present invention will be described.
An image processing apparatus according to the embodiment will be described. In the present embodiment, the filter 1 and the filter 2 have different characteristics depending on the image area.

FIG. 2 is a block diagram of the image processing apparatus according to the present embodiment.

<Reading Unit> The document to be copied is placed on a document table (not shown) of the scanner unit 201 and read. As in the case of FIG. 10, the scanner unit 201 digitally reads a document image for each pixel using a color three-line CCD, and transfers a color image signal to the input image processing unit 202. In the input image processing unit 202, the scanner unit 2
For example, shading correction, CCD line-to-line correction, color correction, etc.
Known image processing is performed.

Reference numeral 203 denotes an image area separation processing unit which performs the following image area separation processing on the input image processed color image signal output from the input image processing unit 202, and Among the characteristics of the pixel, such as a photograph region, a character region, and a halftone dot region, it is detected which region has the characteristic, and flag data representing an attribute of each image region is attached to each pixel.

<Image Area Separation Processing> Here, the image area separation processing section 203 will be described.

The image area separation processing is to extract the characteristics of the original image and perform a signal indicating the image area attribute (hereinafter referred to as flag data) in order to perform the optimal image processing according to the characteristics of the image included in the original image. Is generated. In general, a document contains various image areas such as a continuous-tone full-color photograph area, a solid black character area, and a halftone print area such as newspaper printing. If the same image processing is uniformly applied to an image having these region characteristics, an output image with preferable image quality may not be obtained. Therefore, the image area separation processing unit 203 according to the present embodiment uses the color image signal input from the input image processing unit 202 to detect the attribute of the image data included in the original image and identify the attribute. Of flag data is generated.

FIG. 3 shows an example of a document image.
This shows a state in which a silver halide photograph area 302, a black character area 303, a halftone print area 304, and a color graphic area 305 are mixed in one page 301.

Here, the scanner unit 201 scans the original image by a color CCD sensor and reads it as a color digital signal (RGB signal) for each pixel. The read RGB signals have characteristics determined by the attribute of each region of the image. When the G signal of the RGB signals read by the CCD sensor in each area is graphed in the arrangement direction of the CCD, for example, a curve shown in FIG. 4 is obtained. The horizontal axis in FIG. 4 indicates the pixel position in the CCD arrangement direction, and the vertical axis indicates that the higher the read signal value, the closer to white (brighter) the pixel.

In FIG. 4, reference numerals 402, 403, 404, 405
Are examples of characteristics that appear characteristically when reading the areas 302 to 305 in FIG. The features of each area will be described below.

Since 302 is a photographic area, the change 402 depending on the position of the read image signal is relatively gradual, and the difference 412 from the pixel value at a short distance is a small value.

Reference numeral 303 denotes a black character area in which black characters are written on a white background. The characteristic curve 403 corresponds to the white background portion 41.
The characteristic is such that the read signal value changes rapidly from 3 to the character portion 423.

Reference numeral 304 denotes a halftone dot area in which a white background and a black character are repeated. The characteristic curve 404 has such a characteristic that a white background 414 and a halftone dot 424 repeat at a high frequency. 405 is a diagram showing characteristics of the graphic area 305. At the edge portion 415 of the graphic area, the signal value sharply decreases, and at the inner colored portion 416, a characteristic such that a constant intermediate level continues.

The determination of these attributes can be made by detecting the above-described feature of each area from the read signal value. The determination includes the change amount of the image data in the vicinity of the pixel of interest or the integrated value of the change amount in a certain section, the luminance value of a peripheral pixel (white background or colored background), the whiteness of the image data in the certain section. A known feature extraction method using information such as the number of times of change from black to black and a known attribute discrimination method based on the extracted features can be used.

FIG. 5 shows an example of an attribute flag generated for the document image of FIG. Here, three types of flags, ie, a character flag, a graphic flag, and a halftone flag, are shown as attribute flags (flag data), but are not limited to them. FIG. 5A shows a portion recognized as a pixel having characteristics of a character area. A pixel having a character area characteristic has a character flag set to 1, and other pixels have a character flag set to 0 (white portion in the figure). Similarly, FIG. 5B shows a portion that is recognized as a pixel having the characteristics of the graphic area. For the pixels having the characteristics of the graphic area, the graphic flag is set to 1, and for the other pixels, the graphic flag is set to 0 (white portion in the figure). FIG. 5C shows a portion recognized as a pixel having the characteristics of a halftone dot region. For a pixel having the characteristics of a halftone dot region, a halftone flag is set to 1;
For others, set the dot flag to 0 (white part in the figure)
Is set. Since the photograph area does not correspond to any of these, all the flags are set to 0 and will not appear in FIG.

When the attribute of the image is detected for each pixel by the above-described image area separation processing, the image processing corresponding to the image attribute is performed by the filter 1 at 204. Details of this part will be described later.

<Storage of Image Data> Image data read by the scanner 201 and subjected to various input image processing,
The attribute flag data generated by the above procedure is temporarily stored in the image memory 1 of 205 and the flag memory 1 of 206, respectively. At this time, the image data and the attribute flag data are stored as one whole page of the document or as a partial image of a predetermined size of one page.

The temporarily stored image data and attribute flag data are compressed by the data compression unit 207 and stored in the storage device 208. The storage device 208 is preferably a high-speed storage device such as a semiconductor storage device. The data compression unit performs different data compression processing on the image data and the flag data. In other words, the image data is subjected to a highly efficient compression process that is irreversible, such as JPEG irreversible compression, but in which image degradation in consideration of human visual characteristics is less noticeable, and the flag data is On the other hand, it is desirable to use a reversible compression method such as JPEG reversible compression in order to prevent loss or change of the attribute flag information.

In this way, image data and flag data that have been subjected to different compression processes are stored in the storage device 208 in units of one page of the document. The stored data is
In some cases, data may be written to the auxiliary storage device 209. Desirably, the auxiliary storage device 209 uses a medium, such as a hard disk, which has a slightly lower recording speed but can store a large amount of data. With this configuration,
Document images of many pages can be efficiently stored and accumulated.

<Reading of Image Data> Storage Device 208
Alternatively, the image data and the attribute flag data stored in the auxiliary storage device 209 are read for output to the printing unit, and the compressed data is decompressed by the data decompression unit 210, and the image memory 2 and the 212 is written to the flag memory 2.

At this time, in the pixel density conversion unit 213,
The pixel density of the stored image data is converted as needed. This process is used, for example, when it is desired to print out the stored image data by enlarging or reducing it, or when combining and outputting a plurality of stored pages on one print output sheet.

FIG. 6 shows an example of a composite output of a plurality of pages.
It is assumed that the two original images 601 and 602 in the figure are stored in the storage device in advance. The figure shows an example in which both images are combined into one sheet on output paper of the same size as the document to obtain a print output 603.

In order to obtain a composite output, first, the stored image data 601 is read out from the storage device 208, and the compressed data is decompressed by the data decompression 208. In the pixel density conversion unit 213, the decompressed data is reduced at a predetermined magnification, rotated 90 degrees to the left by a rotation processing unit (not shown), and written in a predetermined area of the image memory 2 indicated by 211 (FIG. 6). 604).

Next, the image data 602 is read out, subjected to the same decompression, resolution conversion, and rotation processing, and written into the area 605 of the image memory 2 indicated by reference numeral 211 where the image data is to be written.

At this time, the flag data corresponding to the originals A and B are similarly decompressed, converted in resolution and rotated, and written in the corresponding area of the flag memory 2 indicated by 212.

Here, it is desirable to apply different methods to the resolution conversion of the image data and the resolution conversion of the flag data, respectively. For example, a method such as a linear interpolation method or a bicubic spline interpolation method is applied to image data, and a resolution conversion method suitable for binary data such as a nearest neighbor processing method is used for resolution conversion of flag data. To

<Output of Image Data> The image data and flag data temporarily stored in the image memory 2 of 211 and the flag memory 2 of 212 reach a predetermined size and are transferred to the correction means 2 of 214.

In the filter 2 at 214, the image data is filtered based on the contents of the flag data. The details will be described later.

After the processing in the filter 2 at 214, the image data is transferred to the output image processing unit 215.

The output image processing unit 215 performs known image processing for printing and outputting RGB image data, that is, processing such as luminance density conversion, RGB → CMYK conversion, gamma correction, and binarization processing. Transfer to the unit 216.

The printer section 216 drives the laser in accordance with the transferred CMYK image signals, and forms and outputs a visible image on transfer paper in the same procedure as in FIG.

Here, the flag data stored in the flag memory 2 of 212 is used for switching the processing of the filter 2 of 214 and the output image processing unit 215.

The processing in the image processing unit 215 includes the following.

For example, in the photograph area and the character area, RGB
→ Perform processing to change the coefficients of CMYK conversion. Thereby, the image quality of the output image can be improved. For example, for a character area, that is, for a pixel having a character flag of 1, a conversion coefficient that allows a black character to be reproduced only with black toner (that is, a coefficient such that C, M, and Y = 0 when image data is achromatic) ) Is applied, C, M, and Y are not set to 0 even in an achromatic color, and the coefficients are changed so that deep black can be reproduced.

In the binarization process, the C, M, Y, and K signals are converted into binary signals of 0 or 1 by using a known error diffusion process or dither process. In the area, the sharpness of the output image is prioritized, so the error diffusion processing is applied. In the photographic area and the halftone dot area, the dither processing is applied because the gradation is important. By switching the contents of the binarization processing based on the attribute flag data in this manner, the image quality of the output image can be improved.

FIG. 7 shows an example of a block diagram of a configuration of a portion for realizing this function. The filter 214 at 214, the flag memory 2 at 212, and the printer unit 216 are the same as those in FIG. RGB read from the image memory 2 of 211
Of color image data of two Rs 701 and 702 in parallel.
The data is input to the GB → CMYK conversion circuit.
It is converted to a MYK image signal. One of the outputs of the RGB → CMYK conversion circuits 701 and 702 is selected by the selector 1 703 according to the flag signal of the flag memory 2 of 212. When a conversion coefficient for a character area is set in the RGB → CMYK conversion circuit 701 and other coefficients are set in the RGB → CMYK conversion circuit 702,
212 when the character flag in the flag memory 2 is 1
The output of the GB → CMYK conversion circuit 701 is selected, and when the character flag is 0, the output of the RGB → CMYK conversion circuit 702 is selected.

The output of the selector 1 at 703 is also separated into two systems in parallel. One of the outputs is passed through a gamma correction circuit 1 at 704 and an error diffusion binarization processing unit at 706 to generate a binary CM.
The YK signal is input to the selector 2 at 708.

The other passes through a gamma correction circuit 2 at 705 and a dither processing binarization circuit at 707 to generate a binary CMYK signal.
The signal is input to the selector 2 at 708.

In the selector 2, the error diffusion binarization processing section 7
06 or the output of the dither processing binarization circuit 707 is selected and transferred to the printer unit. The error diffusion binarization processing unit 706 or the dither processing binarization circuit selects the error diffusion processing in the character area and the graph area. Therefore, when the character flag is 1 or the graphic flag is 1, the selector 2 performs the error diffusion binarization. The output of the processing unit 706 is selected, and if not, the output of the dither processing binarization circuit 707 is selected.

<Filter> As described in the first embodiment, both the filter 1 and the filter 2 are intended to realize a desired frequency characteristic. In general, however, the desired frequency characteristic is also dependent on the attribute of an image. different.

Therefore, as a characteristic obtained by multiplying the two by the filter 1 and the filter 2, for example, the high frequency component of the image is emphasized for the character region to enhance the sharpness of the character, and for the halftone dot region, In this case, characteristics are set such that high-frequency components are dropped and moiré components peculiar to digital images are removed. The switching of these processes can be performed on a pixel-by-pixel basis according to the attribute flag data generated by the image area separation processing unit 203.

As described above, since the filter is divided into the filter 1 and the filter 2, the desired frequency characteristics of each attribute can be distributed to each filter. In these two filters, processing of three systems as shown in FIGS. 8 and 9 is switched in order to realize a desired frequency characteristic for each image area.

FIG. 8 is a diagram relating to the filter 1. In FIG. 8, the image area separation processing unit 203 and the image memory 1 of 205 are the same as those shown in FIG. The RGB data after the image area separation processing is subjected to filter processing of three coefficients in parallel.

Reference numeral 801 denotes a character filter 1 which is a filter having coefficients suitable for compressing a character image. Similarly,
Reference numeral 802 denotes a halftone filter 1, which is a filter having coefficients suitable for compressing a halftone image. Reference numeral 803 denotes a photographic filter 1, which is a filter having coefficients suitable for compressing a photographic image. The image data is subjected to these three filtering processes independently, and is input to the selector 804. Selector 8
Reference numeral 04 denotes a character file 1 (80) based on the flag data read from the image area separation processing unit 203 in pixel units.
1) or the output of the photo file 1 (803) is selected. The output of the selector 804 is 205
Is input to the image memory 1.

FIG. 9 is a diagram relating to file 2. In FIG. 9 as well, the image memory 2 of 211, the flag memory 2 of 212, and the output image processing unit 215 are the same as those shown in FIG. is there. RGB sent from image memory 2
The data is again filtered by three coefficients in parallel.

Reference numeral 901 denotes a character filter 2 having a filter coefficient obtained by removing a characteristic component of the filter 1 from frequency characteristics optimum for filtering a character image. Similarly,
Reference numeral 902 denotes a halftone filter 2, which has a filter coefficient obtained by removing a characteristic component of the filter 1 from a frequency characteristic most suitable for filtering a halftone image, and 903 denotes a photographic filter 2. It has a filter coefficient obtained by removing a characteristic component of the filter 1 from a frequency characteristic optimum for filtering.

The image data is subjected to these three filtering processes independently, and is input to the selector 904. The selector 904 selects, based on the flag data read from the flag memory 2, either the output of the character filter 2 (901) or the output of the photograph filter 2 (903) in pixel units. Then, the output of the selector 904 is input to the output image processing unit 215.

When the pixel density conversion is performed, the coefficients of the filter 1 and the filter 2 can be changed according to the magnification.

The filter 2 may be performed in the CMYK color space after the RGB → CMYK conversion.

As described above, in the embodiment of the present invention, by switching the image area separation processing and the coefficients of the two filters, it is possible to distribute the frequency characteristics according to the attributes of the image to the two filters. And high-quality images can be obtained.

Further, by switching the coefficients of the two filters according to the scaling factor, the frequency characteristics can be distributed according to the scaling factor, and a high-quality image can be obtained even for a scaled image.

[Other Embodiments] Even if the present invention is applied to a system constituted by a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus (one device) For example, the present invention may be applied to a copying machine, a facsimile machine, and the like.

Further, an object of the present invention is to supply a storage medium (or a recording medium) in which program codes of software for realizing the functions of the above-described embodiments are recorded to a system or an apparatus, and to provide a computer (a computer) of the system or the apparatus. Or a CPU or MPU) reads out and executes the program code stored in the storage medium,
Needless to say, this is achieved. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.
In addition, by the computer executing the readout program code, not only the functions of the above-described embodiments are realized, but also based on the instructions of the program code,
The operating system (OS) running on the computer performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

Further, after the program code read from the storage medium is written into the memory provided in the function expansion card inserted into the computer or the function expansion unit connected to the computer, the program code is read based on the instruction of the program code. , The CPU provided in the function expansion card or the function expansion unit performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the processes described above.

[0090]

As described above, according to the present invention, a color image can be copied in a short time without deteriorating the image quality.

That is, it is possible to realize an image system which makes it easy to handle images in the color image processing system, does not impose a great burden on the user, and reduces the capacity of the image storage means. By providing filters before and after, it is possible to obtain high-quality image output without image degradation due to compression.

Further, by switching the image area separation processing and the coefficients of the two filters, it is possible to distribute the frequency characteristics corresponding to the attributes of the image to the two filters, and to obtain a high-quality image. Can be done.

Further, by switching the coefficients of the two filters according to the scaling factor, the frequency characteristics can be distributed according to the scaling factor, and a high-quality image can be obtained even for a scaled image.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an image processing apparatus according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a document image to be read.

FIG. 4 is a diagram illustrating distribution characteristics of an image signal for each image area.

FIG. 5 is a diagram illustrating a portion where flag data becomes 1 for each image area.

FIG. 6 is a diagram illustrating a layout synthesis output.

FIG. 7 is a block diagram illustrating a configuration of an output image processing unit according to a second embodiment of the present invention.

FIG. 8 is a block diagram illustrating a configuration of a filter 1 according to a second embodiment of the present invention.

FIG. 9 is a block diagram illustrating a configuration of a filter 2 according to a second embodiment of the present invention.

FIG. 10 is a diagram schematically illustrating a conventional color image copying apparatus.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/46 H04N 1/46 Z F term (Reference) 5B057 AA11 BA02 CA01 CA08 CA12 CA16 CB01 CB08 CB12 CB16 CC03 CD05 CE01 CE06 CE17 CG01 CH18 DA17 DB02 DB06 DB09 DC22 DC25 5C077 LL19 MM03 MP01 MP02 MP05 MP06 MP07 MP08 NN08 NN11 PP02 PP03 PP20 PP27 PP28 PP32 PP33 PP37 PP47 PP48 PP49 PQ08 PQ20 PQ25 RR02 RR21 TT06 5C078 A09A09 A06A09 A06 LA06 LA15 LA27 MA01 MA02 NA02 NA11 NA17 9A001 EE04 HH27 HH31 JJ35

Claims (8)

[Claims] An image processing apparatus for reading an original image as a digital color image signal and forming an output color image of the original image, wherein a first digital filter process is performed on the color image signal. Filter means, means for image-compressing the color image signal after the digital filter processing, means for storing the color image signal after the image compression, means for expanding the stored color image signal, Second filter means for performing a predetermined digital filter process on the decompressed color image signal, wherein the first filter means is a digital filter for reducing deterioration of the color image signal after image compression. The second filter means performs digital filter processing for reducing deterioration of the decompressed color image signal; An image processing apparatus characterized by forming the output color image based on the color image signal from said second filter means. 2. An image processing apparatus which samples an original image in pixel units and reads it as a digital color image signal to form an output color image of the original image, wherein after the reading, based on a pattern of the color image signal Identification means for identifying the characteristics of the image at each pixel position, flag generation means for generating predetermined flag data in each pixel according to the result of the identification, having a plurality of digital filter characteristics, A first fill means for individually performing fill processing; and a color image signal output from the first fill means for different fill image processing, for each pixel, the First forming means for extracting an image signal and forming a color image signal; and image-compressing the formed color image signal,
Compression means for also compressing the flag data; means for storing the color image signal after the image compression and the flag data after the data compression; and decompressing the stored color image signal and the stored flag data. A second filter means having a plurality of digital filter characteristics and individually performing filter processing; and a color image signal output from the second filter means and having different color image processing, A second forming unit configured to extract the color image signal in accordance with the decompressed flag data for each pixel and form a color image signal, based on the color image signal from the second forming unit. An image processing apparatus for forming the output color image. 3. The first filter means and the second filter means.
3. The image processing apparatus according to claim 1, wherein said filter means changes said plurality of digital filter characteristics in accordance with a scaling factor. 4. An image processing method for reading a document image as a digital color image signal and forming an output color image of the document image, wherein a first digital filter process is performed on the color image signal. Filtering the color image signal after the digital filtering, storing the color image signal after the image compression, expanding the stored color image signal, A second filter step of performing a predetermined digital filter process on the decompressed color image signal, wherein the first filter step is a digital filter that reduces deterioration of the color image signal after image compression. Performing a fill-in process, wherein the second fill-in step reduces degradation of the decompressed color image signal; Performs digital filtering, image processing method characterized by forming the output color image based on the color image signal from said second filter step. 5. An image processing method for sampling a document image on a pixel basis and reading it as a digital color image signal to form an output color image of the document image, wherein after the reading, based on a pattern of the color image signal. An identification step of identifying a feature of an image at each pixel position, a flag generation step of generating predetermined flag data in accordance with the result of the identification for each pixel, and a plurality of digital filter characteristics, A first fill-in step for individually performing fill-in processing; and a color image signal output from the first fill-in step, which is different in the fill-in processing. A first forming step of extracting an image signal and forming a color image signal, and compressing the formed color image signal Rutotomoni,
A compression step of compressing the flag data as well; a step of storing the color image signal after the image compression and the flag data after the data compression; and a step of expanding the stored color image signal and the stored flag data. A second filter step having a plurality of digital filter characteristics and individually performing filter processing; and a color image signal of different filter processing output from the second filter step, A second forming step of extracting the color image signal in accordance with the decompressed flag data for each pixel and forming a color image signal, based on the color image signal from the second forming step An image processing method comprising forming the output color image. 6. The image processing according to claim 4, wherein the first filter step and the second filter step change the characteristics of the plurality of digital filters according to a scaling factor. Method. 7. A computer-readable memory storing a program code for reading an original image as a digital color image signal and performing image processing for forming an output color image of the original image, wherein the computer-readable memory stores Code for executing a first filter step of performing a predetermined digital filter process, code for executing an image compression process of the color image signal after the digital filter process, and a color image signal after the image compression A code for executing a step of expanding the stored color image signal; and a second filter for performing a predetermined digital filtering process on the expanded color image signal. And code for executing the first filter step. The digital filter processing for reducing the deterioration of the color image signal after the image compression is performed, and the code for executing the second filter step is a digital filter processing for reducing the deterioration of the color image signal after the expansion. Computer readable memory comprising code for forming the output color image based on the color image signal from the second filtering step. 8. A computer-readable memory storing a program code for sampling an original image in pixel units, reading the digital image as a digital color image signal, and performing image processing for forming an output color image of the original image. After reading, a code for executing an identification step of identifying an image feature at each pixel position based on the pattern of the color image signal, and predetermined flag data is generated for each pixel according to the identification result. A code for executing a flag generating step, a code for performing a first filtering step having a plurality of digital filter characteristics, and individually performing filtering processing, and a code output from the first filtering step. According to the flag data, for each of the pixels, the color image is obtained from different color image signals having different fill processes. Extracts a signal, and code for performing a first forming step of forming a color image signal, a color image signal the formed with image compression,
A code for executing a compression step of compressing the flag data also, a code for executing a step of storing the color image signal after the image compression and the flag data after the data compression, A code for executing a step of expanding the stored flag data; a code having a plurality of digital filter characteristics and executing a second filter step for individually performing a filter process; A second forming step of extracting the color image signal for each pixel according to the decompressed flag data from the color image signals having different fill processes output from the step, and forming a color image signal. Executing the output color image based on the color image signal from the second forming step. A computer-readable memory, characterized in that it comprises code for forming.